Primary production of Cymodocea nodosa in the Gulf of Trieste (Northern Adriatic Sea): a comparison of methods

Net primary production of Cymodocea nodosa, a common seagrass in the Mediterranean Sea, was monitored in the Gulf of Trieste using 3 techniques. Production ylelds obtained by a method based on changes in biomass and leaf export, as indicated by the presence of leaf scars, were compared with 2 other approaches, a marking technique and the oxygen evolution in situ. In August-September, maximum total standing biomass at 3 stations ranged between 323 and 1020 g dry wt m-2. At the shallowest station, ca 88 % of total biomass was below ground, compared to 61 % at deeper stations. Leaf area indices varied throughout the growing season between 0.12 and 7.24, indicating a distinct seasonal pattern in leaf production. On average up to 10 leaves were produced shoot-' yr-l; export rates of leaf material were highest in summer. Leaf production, as estimated by the leaf scar and marking techniques, ranged from 356 to 692 g dry wt m-2 yr-l. Combined annual rhizome-root production was highest at the shallowest station (234 g dry wt m-2) compared to 72 g dry wt m-2 at deeper stations.